Methods and systems for multi-element linkage for fiber scanning display

ABSTRACT

A multi-element fiber scanner for scanning electromagnetic imaging radiation includes a base having a base plane and a longitudinal axis orthogonal to the base plane and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operatively coupled to at least one electromagnetic radiation source. The multi-element fiber scanner also includes a plurality of additional links joined to the base and extending from the base and a retention collar disposed a predetermined distance along the longitudinal axis from the base. The first fiber link and the plurality of fiber links are joined to the retention collar.

CROSS-REFERENCES TO RELATED APPLICATIONS

This Application claims priority to U.S. Provisional Patent ApplicationNo. 62/438,415, filed on Dec. 22, 2016, entitled “Methods and Systemsfor Multi-Element Linkage for Fiber Scanning Display,” the disclosure ofwhich is hereby incorporated by reference in its entirety for allpurposes.

The following regular U.S. Patent Applications (including this one) arebeing filed concurrently, and the entire disclosure of the otherapplications are incorporated by reference into this application for allpurposes:

U.S. patent application Ser. No. 15/851,005, filed Dec. 21, 2017,entitled “SHAPED FIBER ELEMENTS FOR SCANNING FIBER DISPLAYS;”

U.S. patent application Ser. No. 15/851,049, filed Dec. 21, 2017,entitled “METHODS AND SYSTEMS FOR FABRICATION OF SHAPED FIBER ELEMENTSUSING LASER ABLATION;” and

U.S. patent application Ser. No. 15/851,317, filed on Dec. 21, 2017,entitled “METHODS AND SYSTEMS FOR MULTI-ELEMENT LINKAGE FOR FIBERSCANNING DISPLAY.”

BACKGROUND OF THE INVENTION

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a viewer in a manner wherein they seem to be,or may be perceived as, real. A virtual reality, or “VR,” scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR,” scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the viewer.

Despite the progress made in these display technologies, there is a needin the art for improved methods and systems related to augmented realitysystems, particularly, display systems.

SUMMARY OF THE INVENTION

The present invention relates generally to methods and systems relatedto fiber scanning projection display systems. More particularly,embodiments of the present invention provide methods and systems formulti-element linkages that enable scanned fibers to oscillate in aplane, in a set of planes, or along an arc. The invention is applicableto a variety of applications in computer vision and image displaysystems.

According to an embodiment of the present invention, a multi-elementfiber scanner for scanning electromagnetic imaging radiation isprovided. The multi-element fiber scanner includes a base having a baseplane and a longitudinal axis orthogonal to the base plane and a firstfiber link passing through the base in a direction parallel to thelongitudinal axis. The first fiber link is operatively coupled to atleast one electromagnetic radiation source. The multi-element fiberscanner also includes a plurality of additional links joined to the baseand extending from the base and a retention collar disposed apredetermined distance along the longitudinal axis from the base,wherein the first fiber link and the plurality of fiber links are joinedto the retention collar. The plurality of additional links can extendfrom the base in a direction substantially parallel to the longitudinalaxis. During operation, the multi-element fiber scanner can scan theelectromagnetic imaging radiation along an axis parallel to the baseplane.

According to another embodiment of the present invention, a method offabricating a multi-element fiber scanner is provided. The methodincludes providing a fiber optic cable having a cladding region and afiber core and focusing a laser beam at a series of predeterminedlocations inside the cladding region of the fiber optic cable. Themethod also includes creating a plurality of damage sites at thepredetermined locations, exposing the fiber optic cable to an etchantsolution, and preferentially etching the plurality of damage sites toform a base having a base plane and a longitudinal axis orthogonal tothe base plane, a retention collar disposed a predetermined distancealong the longitudinal axis from the base, a first fiber link includingthe fiber core, passing through the base plane, and joined to theretention collar, and a plurality of additional links joined to thebase, extending from the base to the retention collar, and joined to theretention collar.

As an example, the method can further include rotating the fiber opticcable around the longitudinal axis during the creating the plurality ofdamage sites at the predetermined locations. Moreover, creating theplurality of damage sites at the predetermined locations can includeforming a latticework of damage sites, which can include a plurality ofradial vias passing through the cladding region towards the fiber core.In one implementation, creating the plurality of damage sites at thepredetermined locations includes initially creating a first portion ofthe plurality of damage sites adjacent the fiber core and subsequentlycreating a second portion of the plurality of damage sites adjacent aperiphery of the cladding region. In addition to a fiber cladding and afiber core, the fiber optic cable can include a plurality of sacrificialregions disposed in the cladding region. The plurality of sacrificialregions can be air cavities or can include a material having a higheretch rate than the cladding region.

According to a specific embodiment of the present invention, a method offabricating a multi-element fiber scanner is provided. The methodincludes fabricating a preform including structural precursors for atleast one fiber waveguide, fiber supports, and sacrificial material anddrawing the preform to form a fiber structure. The method also includesexposing the fiber structure to an etchant solution and preferentiallyetching the sacrificial material to form: a base having a base plane anda longitudinal axis orthogonal to the base plane, a retention collardisposed a predetermined distance along the longitudinal axis from thebase, a first fiber link including the at least one fiber waveguide,passing through the base plane, and joined to the retention collar, anda plurality of fiber supports joined to the base, extending from thebase to the retention collar, and joined to the retention collar.

According to another specific embodiment of the present invention, amethod of operating a multi-element fiber scanner is provided. Themethod includes providing a source of electromagnetic radiation anddirecting electromagnetic radiation from the source through a firstfiber link. The first fiber link passes through a base having a baseplane and a longitudinal axis orthogonal to the base plane. The methodalso includes supporting a retention collar disposed a predetermineddistance along the longitudinal axis from the base. A plurality ofadditional links join the base and the retention collar. The methodfurther includes translating the base in the base plane, translating theretention collar in a set of planes parallel to the base plane, andscanning the electromagnetic radiation in one or more axes.

According to a particular embodiment of the present invention, amulti-element fiber scanner for scanning electromagnetic imagingradiation is provided. The multi-element fiber scanner includes a basehaving a base plane and a longitudinal axis orthogonal to the base planeand a first fiber link passing through the base in a direction parallelto the longitudinal axis. The first fiber link is operatively coupled toat least one electromagnetic radiation source. The multi-element fiberscanner also includes a plurality of actuation elements joined to thebase and extending from the base along the longitudinal axis and aretention collar disposed a predetermined distance along thelongitudinal axis from the base. The plurality of actuation elements canbe arrayed surrounding the first fiber link. The first fiber link andthe plurality of actuation elements are joined to the retention collar.During operation, the first fiber link is operable to scan theelectromagnetic imaging radiation along an axis parallel to the baseplane.

According to another particular embodiment of the present invention, amethod of operating a multi-axis fiber scanner is provided. The methodincludes providing a source of electromagnetic radiation and directingelectromagnetic radiation from the source through a first fiber link.The first fiber link passes through a base having a base plane and alongitudinal axis orthogonal to the base plane. The method also includessupporting a retention collar disposed a predetermined distance alongthe longitudinal axis from the base. A plurality of piezoelectricactuators join the base and the retention collar. A first piezoelectricactuator of the plurality of piezoelectric actuators joins one side ofthe base to one side of the retention collar. A second piezoelectricactuator of the plurality of piezoelectric actuators joins an opposingside of the base to an opposing side of the retention collar. The firstpiezoelectric actuator and the second piezoelectric actuator lie in ascanning plane. The method further includes actuating the firstpiezoelectric actuator of the plurality of piezoelectric actuators todecrease the distance from the one side of the base to the one side ofthe retention collar, actuating the second piezoelectric actuator of theplurality of piezoelectric actuators to increase the distance from theopposing side of the base to the opposing side of the retention collar,and scanning the first fiber link in the scanning plane. As describedherein, the methods can include alternately actuating a first of thepiezoelectric actuators to decrease or increase the distance at one sidebetween the base and the retention collar while synchronouslyalternately actuating the second of the piezoelectric actuators toincrease or decrease the distance on a second side between the base andthe retention collar.

According to another embodiment of the present invention, amulti-element fiber scanner for scanning electromagnetic imagingradiation is provided. The multi-element fiber scanner includes a basehaving a base plane and a longitudinal axis orthogonal to the base planeand a first fiber link passing through the base in a direction parallelto the longitudinal axis. The first fiber link is operatively coupled toat least one electromagnetic radiation source. The multi-element fiberscanner also includes a plurality of motion actuation links joined tothe base and extending from the base. Each of the plurality of motionactuation links includes a first piezoelectric element proximate to thebase and a second piezoelectric element coupled to the firstpiezoelectric element at a location distal from the base. Themulti-element fiber scanner further includes a retention collar disposeda predetermined distance along the longitudinal axis from the base. Thefirst fiber link and the second piezoelectric element of each of theplurality of motion actuation links are joined to the retention collar.During operation, the first piezoelectric element contracts/expands asthe second piezoelectric element expands/contracts.

According to yet another embodiment of the present invention, amulti-element fiber scanner for scanning electromagnetic imagingradiation is provided. The multi-element fiber scanner includes a basehaving a support surface defining a base plane, a mounting surfaceopposing the support surface, and a longitudinal axis orthogonal to thebase plane and a plurality of motion actuators coupled to the supportsurface of the base. The multi-element fiber scanner also includes amulti-link fiber structure coupled the mounting surface. The multi-linkfiber structure includes a fiber base and a fiber link passing throughthe fiber base in a direction parallel to the longitudinal axis. Thefiber link is operatively coupled to at least one electromagneticradiation source. The multi-link fiber structure also includes aplurality of motion actuation elements (e.g., piezoelectric actuators)joined to the fiber base and extending from the fiber base along thelongitudinal axis and a retention collar disposed a predetermineddistance along the longitudinal axis from the fiber base. The fiber linkand the plurality of motion actuation elements are joined to theretention collar.

Numerous benefits are achieved by way of the present invention overconventional techniques. For example, embodiments of the presentinvention provide methods and systems that scan an optical fiber supportin a substantially planar manner, thereby providing an image fieldhaving a known profile. These and other embodiments of the inventionalong with many of its advantages and features are described in moredetail in conjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified perspective drawing illustrating a multi-elementfiber scanner according to an embodiment of the present invention.

FIG. 2 is a simplified drawing illustrating two scanning positions for amulti-element fiber scanner according to an embodiment of the presentinvention.

FIG. 3 is a simplified drawing illustrating a multi-element fiberscanner with tilted links according to an embodiment of the presentinvention.

FIG. 4 is a simplified drawing illustrating elements of a fiber scanningsystem according to an embodiment of the present invention.

FIG. 5 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to an embodiment of the presentinvention.

FIG. 6 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to another embodiment of thepresent invention.

FIG. 7 is simplified flowchart illustrating a method of operating amulti-element fiber scanner according to an embodiment of the presentinvention.

FIG. 8A is a simplified perspective drawing illustrating a multi-axisfiber scanner according to an embodiment of the present invention.

FIG. 8B is a simplified flowchart illustrating a method of operating amulti-axis fiber scanner according to an embodiment of the presentinvention.

FIG. 9A is a simplified side view illustrating a multi-section motionactuation element according to an embodiment of the present invention.

FIG. 9B is a simplified side view illustrating an oscillatory motion ofthe multi-section motion actuation element illustrated in FIG. 9Aaccording to an embodiment of the present invention.

FIG. 9C is a simplified side view illustrating a multi-element fiberscanner with the multi-element motion actuation element illustrated inFIG. 9A according to an embodiment of the present invention.

FIG. 9D is a simplified perspective view of a piezoelectric motionactuator according to an embodiment of the present invention.

FIG. 9E is a simplified end view illustrating a multi-element motionactuator according to an embodiment of the present invention.

FIG. 9F is a simplified side view illustrating a multi-section motionactuation structure according to an embodiment of the present invention.

FIG. 10 is a multi-element fiber scanner for scanning electromagneticimaging radiation according to an embodiment of the present invention.

FIG. 11 is a simplified side view of a fiber optic cable and laserablation beams according to an embodiment of the present invention.

FIG. 12 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Embodiments of the present invention relate to methods and systemsrelated to fiber scanning projection display systems. More particularly,embodiments of the present invention provide methods and systems formulti-element linkages that enable scanned fibers to oscillate in aplane or along an arc. The invention is applicable to a variety ofapplications in computer vision and image display systems.

FIG. 1 is a simplified perspective drawing illustrating a multi-elementfiber scanner according to an embodiment of the present invention. Themulti-element fiber scanner 100 can be used to scan electromagneticimaging radiation, thereby forming an element of a display system. Themulti-element fiber scanner includes a base 110, which can also bereferred to as an actuator base. The base is disposed in a base planeand can be characterized by a longitudinal axis 112 that is orthogonalto the base plane.

The multi-element fiber scanner also includes a retention collar 130that is disposed a predetermined distance D along the longitudinal axis112 from the base 110. In some embodiments, the retention collar 130 isparallel to the base and orthogonal to the longitudinal axis. The regionbetween the base 110 and the retention collar 130 can be referred to asa pillar section.

A first fiber link 114, which can also be referred to as a waveguide,passes through the base in a direction parallel to the longitudinalaxis. The first fiber link 114 is operatively coupled to at least oneelectromagnetic radiation source (not shown) so that modulated light canbe directed through the first fiber link while a distal end of the fibertip is mechanically scanned in order to generate an image, which canthen be coupled through a display system. The first fiber link can befixed to the base at the location through which it passes through thebase or may be free to move in the base plane. The first fiber linkpasses through the retention collar and can be fixed to the retentioncollar at the location through which it passes through the retentioncollar or may be free to move in the plane of the retention collarand/or free to move in the direction parallel to the longitudinal axis(i.e., axially). In some embodiments, the first fiber link passesthrough the retention collar in the direction parallel to thelongitudinal axis.

In alternative embodiments, the first fiber link can be replaced withanother optical waveguide structure that can be fabricated usingprocesses other than fiber drawing processes, for example, using amicro-electro-mechanical system (MEMS) or amicro-opto-electro-mechanical system (MOEMS) microfabrication process.Thus, molded parts and optical waveguides fabricated using additivemanufacturing are included within the scope of the present invention,for example, cantilevered structures, channel waveguides, and the like.These optical waveguide structures can be fabricated from a variety ofmaterials including silicon, silicon carbide, silicon oxides, siliconnitrides, combinations thereof, and the like.

In addition to the first fiber link, a plurality of additional links 116extend from the base. These addition links, which can be fabricated fromglass materials, are joined at one end to the base and at the other endto the retention collar. As a result, the retention collar ismechanically joined to the additional links. The plane in which theretention collar is disposed can be considered as one of a set of motionplanes since the retention collar will oscillate as it moves throughthis set of planes. In the embodiment illustrated in FIG. 1, theplurality of additional links are arrayed surrounding the first fiberlink, but this is not required by the present invention. In otherembodiments, the number and position of each of the addition links ismodified as appropriate to the particular application. Moreover,although the plurality of additional links illustrated in FIG. 1 extendfrom the base in the direction parallel to the longitudinal axis, thisis not required by the present invention as described more fully inrelation to FIG. 3.

The additional links can provide just mechanical functionality or canalso provide optical functionality. As an example, the additional linkscan be replaced with piezoelectric elements that can expand and contractto provide motion actuation. In these embodiments, one or more of theplurality of additional links can be operatively coupled to the at leastone electromagnetic radiation source, or other electromagnetic radiationsources, and pass through the base parallel to the longitudinal axis andthrough the retention collar. In these embodiments, modulated light canbe delivered through all of the fiber links providing opticalfunctionality. It should be appreciated that the additional links can befabricated in various manners and using various materials. Although someembodiments are described in terms of glass links fabricated from afiber optic, the present invention is not limited to this material ormethod of manufacture and other materials and fabrication processes canbe used in relation to the additional links.

Multiple core fiber scanners provide an array of sources associated withmultiple pixels that can be scanned to produce the displayed image witha multiplied resolution as a function of the number of sources. In someembodiments, one set of the additional links is used for mechanicalsupport and another set is used as additional light sources tocomplement the first fiber link. Thus, embodiments of the presentinvention include implementations with a single fiber core andmechanical supports (e.g., a plurality of peripheral supports), multiplefiber cores and mechanical supports, and multiple fiber cores providingboth optical and mechanical functionality. The mechanical supports canbe made of glass similar to the first fiber core or of other suitablematerials with sufficient flexibility and rigidity, includingpiezoelectric materials, metals, ceramics, polymers, or the like. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

In an alternative embodiment, multiple fiber cores terminating atdifferent longitudinal positions can be implemented in conjunction withthe fiber scanners described herein. In this embodiment, the depth planeassociated with each of the fiber cores can be varied to providedifferent signals at different depths.

Referring to FIG. 1, the multi-element fiber scanner can also include apiezoelectric actuator 105 that is mechanically coupled to the base 110.The piezoelectric actuator is operable to translate the base in the baseplane, for example, laterally along direction 107 or in a transversedirection pointing into and out of the plane of the figure. As anexample, the piezoelectric actuator 105, which can also be referred toas a base, could include multiple piezoelectric elements that cancontract and expand as appropriate to produce the desired oscillationsin the base. In embodiments in which the base is translated laterally,the first fiber link is scanned laterally in the plane of the figure andthe electromagnetic imaging radiation is scanned along an axis parallelto the base plane. The light rays 115 emitted from the first fiber linkare illustrated as light leaves the optical fiber 114.

Since the additional links are mechanically coupled to each other inboth the base plane and the plane of the retention collar, motion of thebase in the base plane, for example, using a piezoelectric actuator 105,will result in motion of the tops of the additional links, and theretention collar, in a set of planes parallel to the plane of theretention collar.

FIG. 2 is a simplified drawing illustrating two scanning positions for amulti-element fiber scanner according to an embodiment of the presentinvention. As illustrated in FIG. 2, motion of the base 110 in the baseplane will result in motion of the retention collar 130 horizontally(and vertically in some implementations). Two positions of the retentioncollar are shown, illustrating ends of an exemplary range of motion. Ata center position in which the retention collar is directly above thebase, the retention collar will be separated from the base by a greatervertical distance than at the illustrated positions. However, for smallangles (e.g., angles less than several degrees), the variation indistance between the base and the retention collar will be small,resulting in motion of the retention collar in substantially a singleplane that is parallel to the base plane, which can be referred to as amotion plane. As the additional fiber links tilt and/or bend in responseto motion of the base because of the mechanical coupling of the tops ofthe additional links to the retention collar, the retention collarremains parallel to the base plane. The shearing motion illustrated inFIG. 2 is desirable from an optical point of view because the imagefield associated with the first fiber link can be substantially flat,which is useful in various optical configurations, or curved in apredetermined manner. Although additional fiber links are illustrated inFIG. 2, embodiments of the present invention can utilize other materialsand structures for the additional links. As an example, MEMS structurescan be utilized to provide the benefits inherent in embodiments of thepresent invention. Thus, the references to additional links, linkages,and the like should be understood to include MEMS structure including,without limitation, silicon flexures.

FIG. 3 is a simplified drawing illustrating a multi-element fiberscanner with tilted links according to an embodiment of the presentinvention. Referring to FIG. 3, a base 110 is provided to which fiberlinks 310 and 312 are mechanically attached. Electromagnetic radiationsource 330 (e.g., a diode laser or light emitting diode) is opticallycoupled to first fiber link 114. In the embodiment illustrated in FIG.3, fiber link 312 is optically coupled to an electromagnetic radiationsource 331. Thus, depending on the implementation, one or more of theplurality of additional links can pass through the base in a directionsubstantially parallel to the longitudinal axis and can be operativelycoupled to one or more electromagnetic radiation sources. The fiber link310 extends from the base at an angle θ and the fiber link 312 extendsfrom the base at an opposing angle −θ such that both fiber links aretilted towards the first fiber link 114. The fiber links 310 and 312 aremechanically coupled to the retention collar 130. The first fiber link114 can be fixed to the retention collar or can have a sliding fit inthe retention collar.

Because of the tilt present in the fiber links 310 and 312, for smallangles, for example, angles less than about several degrees, the motionof the retention collar 130 (and the fiber tip as a result) will followan arc 320 that has a center coincident with the intersection point R oflines extending from the fiber links. In other words, the radius ofcurvature of the arc 320 is equal to r. Thus, the retention collar inthis configuration translates along a curved arc, which can also bereferred to as a curved oscillation section. As the retention collaroscillates, the light from the first fiber link 114 is emitted towardthe intersection point R at the center of the arc, which can be referredto as a focal point. Thus, in comparison with some systems in which theemission fiber moves through a convex image field, embodiments of thepresent invention move the emission fiber though a concave image fieldsuch as arc 320. At large angles, the fiber tip may deviate from arc 320and such deviations can be compensated for by modification of the opticsdesign. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

In an embodiment, in addition to the first fiber link 114, each of thefiber links 310 and 312 carry optical signals, enabling, in thisexample, three fiber cores each emitting a beam, all of which aredirected toward the focal point. Fabrication of this structure can startwith a preform that includes structural precursors of the fiber links inthe form of cylinders of a first material embedded in a larger cylinderof a second material that is more readily etched. In order to fabricatethis structure, a two-step process can be used in which a first thermaldrawing process is used to draw the preform in a tapered manner suchthat the outer or peripheral fiber cores are tilted towards the centralfiber core. A subsequent laser ablation/selective etching process canthen be used to remove the second material from the pillar region.Alternatively, the embodiment shown in FIG. 3 can be assembled fromdiscrete components.

The fiber links 114, 310, and 312 can include optical fibers. They canbe fabricated using methods known to those skilled in the art, such asthermal drawing. In an embodiment, the retention collar 130 and/or base110 include a silicon, silica, or metal disk, with through holes for thefiber links. The fiber links can be coupled to the retention collar orbase using adhesive, water glass, frit glass, or a metal bond. Fritglass may be applied to the connection as a preform (e.g., toroidal andsurrounding the fiber) to facilitate consistent fabrication. Metal, suchas gold, may be deposited on the fiber, retention collar, and/or baseusing, for instance, an evaporation process. A deformable microbumpstructure may be applied to one of the surfaces to facilitate ametal-to-metal bond under mechanical pressure. Alternatively, themetal-to-metal bond may be formed using heat. In an embodiment, thefibers are inserted through and bonded to the retention collar, andsubsequently ground and polished as a unit, to ensure co-planarterminations of the optical waveguides.

From an optical point of view, the embodiment illustrated in FIG. 3provides benefits not available using conventional techniques. FIG. 4 isa simplified drawing illustrating elements of a fiber scanning systemaccording to an embodiment of the present invention. As illustrated inFIG. 4, the projection system includes an electromagnetic radiationsource 421 (e.g., a diode laser) optically coupled to first fiber link415 and a ball lens 410 into which the light from the first fiber linkis directed. The ball lens 410 can be positioned at approximately theintersection point or focal point R illustrated in FIG. 3 and can covera large field of view while using a compact optical system. The balllens could image the light from the fiber into an eyepiece of a displaysystem. In addition to ball lenses, other entrance pupils of the opticalsystem can be utilized as the focal point. As the first fiber link andthe retention collar sweep through arc 405, the light emitted by thefirst fiber link is directed toward the ball lens or entrance pupil fromall oscillation positions 420, 422, and 424. The tilting of the fibertip towards ball lens 410 enables the use of optical elements that areless costly than what would otherwise be required if the fiber tiptilted away from the center as it moved toward the ends of the range ofmotion.

The structure of the multi-element fiber scanner is amenable to use ofthe laser ablation and laser sculpting techniques described in U.S.Provisional Patent Application No. 62/438,408, titled “Methods andSystems for Fabrication of Shaped Fiber Elements Using Laser Ablation”,filed on Dec. 22, 2016, the disclosure of which is hereby incorporatedby reference. As an example, starting with a multicore fiber preform,the preform could be drawn to form the fiber, and laser ablation andetching can be used to remove material from the pillar section, leavingbehind the desired fiber links. The base and/or the retention platecould be formed of glass out of the original drawn fiber.

FIG. 11 is a simplified side view of a fiber optic cable and laserablation beams according to an embodiment of the present invention. Alaser beam is provided and propagates towards lens 1110, which focusesthe laser beam to a focus spot 1120 inside the cladding 1115 of opticalfiber 1125. Focusing of the laser beam at the focus spot results increation of a damage site at the focus spot. By rotating the fiber alongthe longitudinal axis of the fiber, which is aligned with the fibercore, a series of damage sites can be created at a given radialdistance.

Movement of the laser beam, and associated optical elements, isillustrated in FIG. 11 as the laser beam is moved longitudinally to asecond location such that a second focus spot 1130 is formed at agreater distance from the surface of the fiber. Upon rotation of thefiber around the longitudinal axis, a series of damage sites are createdthat have a smaller radial distance from the fiber core than the seriesof damage sites associated with focus spot 1120. A third longitudinalposition is also illustrated in FIG. 11, forming third focus spot 1140.Using this process, a series 1150 of damage sites, illustrated by adashed profile that is tapered in this embodiment, are created that aresubstantially continuous.

In some embodiments, the lens is moved to adjust the position of thefocused spot, whereas in other embodiments, the focal power of the lenscan be adjusted so the focused spot moves while the lens remains insubstantially the same position. The use of the term substantially isused because focal power changes often result from moving elementsinside the lens (e.g. a camera zoom lens).

As described below, an etching process can be used to preferentiallyetch along the series of damage sites, forming a tapered fiber profilein the embodiment illustrated in FIG. 11 and separating the portion ofthe fiber cladding at radial distances greater than the series of damagesites.

In some embodiments, as the light propagates into the fiber toward thefiber core, the fiber acts as a cylindrical lens in the directionextending into the figure. In the plane of the figure, the fiber doesnot introduce any focusing effect. The cylindrical lensing introduced bythe fiber may adversely impact the size of the focus point at which theseries 1150 of damage sites are created. Accordingly, an astigmatic lenscan be incorporated in the optical path along which the laser beampropagates. As an example, a cylindrical lens could be used asastigmatic lens to introduce correction in the plane extending into thefigure to compensate for focusing by the fiber. In some implementations,the astigmatic lens and/or the lens 1110 have variable opticalparameters so that the amount of astigmatism introduced and/or the focallength can be adjusted during operation of the system.

In some embodiments, separate lenses can be combined into a single lens,which may be a multiple element compound lens, that both focuses thelaser light into the fiber and provides astigmatic pre-correction tocompensate for the cylindrical focusing occurring in the fiber.

FIG. 12 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to an embodiment of the presentinvention. The method described in relation to FIG. 12 is applicable tothe fabrication of a variety of structures described herein, including amulti-element fiber scanner having a base, a retention collar, a firstfiber link including a fiber core and a fiber cladding, and a pluralityof additional links coupling the base to the retention collar. Themethod 1200 includes providing a fiber optic cable (1210), focusing alaser beam at a predetermined location inside the fiber optic cable(1212), and creating a damage site at the predetermined location (1214).

The method also includes focusing the laser beam at a series ofadditional predetermined locations inside the fiber optic cable (1216)and creating a plurality of additional damage sites at the additionalpredetermined locations (1218). In another embodiment, the damage siteand the additional damage sites define a multi-element structureincluding waveguiding elements and mechanical support elements asillustrated in FIGS. 1, 3, 8A, and 10. The mechanical support elementscan include a base and a retention collar as well as mechanical supportscoupled between the base and the retention collar. In an embodiment, thedamage site and the additional damage sites define a tapered profilethat has a decreasing diameter as a function of longitudinal distancetoward the fiber emission tip, thereby producing a tapered fiber.

The method further includes exposing the fiber optic cable to an etchantsolution (1220), preferentially etching the damage site and theplurality of additional damage sites (1222), and separating a portion ofthe fiber optic cable to release the elements of the multi-element fiberscanner (1224). After the preferential etching process, a portion of thestructure can include waveguiding elements such as one or more fiberelements having a fiber core and fiber cladding as well as mechanicalstructures.

According to an embodiment of the present invention, focusing of lightby the fiber as the laser beam propagates to the focus point/damage siteand the plurality of additional damage sites is compensated for by usingan astigmatic lens that introduces an amount of focusing equal andopposite to the focusing that occurs as the laser beam propagatesthrough the fiber. Since the damage sites will be positioned at varyingdepths in the fiber cladding, that is, varying distances from the coreof the fiber, the correction lens can be adjusted as the laser traversesthrough different radial distances in the cladding of the fiber in someimplementations.

In some embodiments, creating the plurality of additional damage sitesat the additional predetermined locations can include forming alatticework of damage sites in the cladding of the fiber optic cable.For example, in some embodiments, a plurality of radial vias can passthrough the cladding region toward the fiber core. The focus point ofthe laser beam can be controlled so that initially, a first portion ofthe plurality of additional damage sites are created adjacent the fibercore (i.e., at small radial distances from the fiber core) andsubsequently, a second portion of the plurality of additional damagesites are created at farther distances from the fiber core (i.e., atlarger radial distances up to the diameter of the cladding region). Thistechnique provides damage free materials through which the laser beampropagates, reducing or preventing degradation in beam quality.

The fiber core is characterized by a longitudinal axis and the methodcan include rotating the fiber around the longitudinal axis while theplurality of additional damage sites are created at the additionalpredetermined locations. Although FIG. 11 illustrates the fiber opticcable as substantially homogeneous material, the fiber optic cable caninclude a cladding region and a plurality of sacrificial regionsdisposed in the cladding region. The plurality of sacrificial regionscan include a material having a higher etch rate than the claddingregion or may be air cavities through which etchant can flow.

It should be appreciated that the specific steps illustrated in FIG. 12provide a particular method of fabricating a multi-element fiber scanneraccording to an embodiment of the present invention. Other sequences ofsteps may also be performed according to alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps outlined above in a different order. Moreover, the individualsteps illustrated in FIG. 12 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 5 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to an embodiment of the presentinvention. The method 500 of fabricating the multi-element fiber scannerincludes providing a fiber optic cable having a cladding region and afiber core (510), focusing a laser beam at a series of predeterminedlocations inside the cladding region of the fiber optic cable (512), andcreating a plurality of damage sites at the predetermined locations(514). Creating the plurality of damage sites at the predeterminedlocations can include forming a latticework of damage sites, a pluralityof radial vias passing through the cladding region towards the fibercore, or the like. In one implementation, the process of creating theplurality of damage sites at the predetermined locations can beperformed by initially creating a first portion of the plurality ofdamage sites adjacent the fiber core and subsequently creating a secondportion of the plurality of damage sites adjacent a periphery of thecladding region.

The method also includes exposing the fiber optic cable to an etchantsolution (516) and preferentially etching the plurality of damage sites(518) to form a base having a base plane and a longitudinal axisorthogonal to the base plane, a retention collar disposed apredetermined distance along the longitudinal axis from the base, afirst fiber link including the fiber core, passing through the baseplane, and joined to the retention collar, and a plurality of additionalfiber links joined to the base, extending from the base to the retentioncollar, and joined to the retention collar.

According to an embodiment of the present invention, the method can alsoinclude rotating the fiber optic cable around the longitudinal axisduring the process of creating the plurality of damage sites at thepredetermined locations. In some implementations, the fiber optic cablecan be fabricated such that it includes a plurality of sacrificialregions disposed in the cladding region that are made using a materialthat has a higher etch rate than the cladding region, enabling thesacrificial material to be preferentially removed. The sacrificialregions can alternatively include air cavities or a combination ofsacrificial material and air cavities.

FIG. 6 is a simplified flowchart illustrating a method of fabricating amulti-element fiber scanner according to another embodiment of thepresent invention. The method 600 of fabricating a multi-element fiberscanner includes fabricating a preform including at least one fiberwaveguide, fiber supports, and sacrificial material (610) and drawingthe preform to form a fiber structure (612).

In the fiber pulling process, fiber preform can include sacrificialregions that can include material with a lower etch resistance than thematerials utilized to define the first fiber link and the plurality ofadditional links or other mechanical supports. As an example, the firstfiber link and the plurality of additional links can be resistant toetching, for example, etching by sulfuric acid or other suitableetchants, while the sacrificial regions, which can be doped or otherwiseprovided to lower their etch resistance (which have etch rates thatdepend on concentration and type of dopant as well as the etchant), canbe etched by sulfuric acid. In various embodiments, the dopant caninclude one or more of fluorine, fluoride, germanium, boron,phosphorous, gallium, indium, arsenic, and antimony. In someembodiments, the etch rate of the fiber link and/or the plurality ofadditional links can be dependent on the purity of the glass (e.g.,sodium/boron/phosphate content) as well as whether the glass has beenannealed.

The method also includes exposing the fiber structure to an etchantsolution (614) and preferentially etching the sacrificial material (616)to form a base having a base plane and a longitudinal axis orthogonal tothe base plane, a retention collar disposed a predetermined distancealong the longitudinal axis from the base, a first fiber link includingthe at least one fiber waveguide, passing through the base plane, andjoined to the retention collar, and a plurality of fiber supports joinedto the base, extending from the base to the retention collar, and joinedto the retention collar.

The base and the retention collar can be masked off to protect themduring the etching process during the preferential sacrificial etchingprocess. The materials can be selected for their mechanical propertiesin addition to their optical properties. Thus, in some embodiments, thebase and retention collar can be excluded from laser damage treatment inorder to reduce their susceptibility to etching.

FIG. 7 is simplified flowchart illustrating a method of operating amulti-element fiber scanner according to an embodiment of the presentinvention. As described below, when the actuator base is translatedlaterally in the base plane, the retention collar translates laterallyin a set of planes as it oscillate. For small angles, the fiber tips areoscillating in substantially a single plane, which provides a flat imagefield. In some embodiments, the fiber tips oscillate in a set of planeswhile maintaining the fiber tip in a longitudinal orientation. Themethod 700 of operating a multi-element fiber scanner includes providinga source of electromagnetic radiation (710) and directingelectromagnetic radiation from the source through a first fiber link(712). The first fiber link passes through a base having a base planeand a longitudinal axis orthogonal to the base plane.

The method also includes supporting a retention collar disposed apredetermined distance along the longitudinal axis from the base (714).A plurality of additional links join the base and the retention collarin some embodiments. One or more of the plurality of additional linkscan pass through the base. In this case, the method can includedirecting the electromagnetic radiation from the source (or from anothersource) through the one or more of the plurality of additional links.The electromagnetic radiation can be modulated in intensity to presentan image.

The method further includes translating the base in the base plane(716), translating the retention collar in a set of planes parallel tothe base plane (718), and scanning the electromagnetic radiation in oneor more axes (720). Considering the motion of the retention collar, thepresent invention includes motion lying substantially in the plane ofthe retention collar for small angles. Thus, for these examples, as theretention collar oscillates laterally, it may move in the longitudinaldirection out of the original plane by small amounts at the end of therange of motion. As an example, the vertical deviation from the originalposition of the retention collar may be in the range of microns tomillimeters, for example, 500 μm or more, in some embodiments. As theangle of oscillation and the range of motion increases, the motion ofthe retention collar is defined by a set of planes parallel to the baseplane and including vertical variation as the retention collar movesboth laterally and longitudinally. As described herein, since theretention collar moves in planes parallel to the base plane, the fibertip is oriented in the longitudinal direction during motion, providingbenefits in relation to the design of the optical imaging system.

In an embodiment, translating the base in the base plane is performed byactuating the base in a first direction and actuating the base in asecond direction orthogonal to the first direction to provide fortwo-dimensional motion. Translating the retention collar in the set ofplanes parallel to the base plane can include tilting the plurality ofadditional links.

FIG. 8A is a simplified perspective drawing illustrating a multi-axisfiber scanner according to an embodiment of the present invention. Themulti-element fiber scanner can be used for scanning electromagneticimaging radiation. The multi-element fiber scanner 800 includes a base110 having a base plane and a longitudinal axis orthogonal to the baseplane. The multi-element fiber scanner also includes a first fiber link114 passing through the base in a direction parallel to the longitudinalaxis. The first fiber link is operatively coupled to at least oneelectromagnetic radiation source (not shown) at a location below thebase 110.

Additionally, the multi-element fiber scanner includes a plurality ofactuation elements 810 joined to the base 110 and extending from thebase along the longitudinal axis, for example, parallel to thelongitudinal axis. The plurality of actuation elements can independentlyexpand 812 and contract 814. The use of opposing actuation elements 810as illustrated in FIG. 8A enables independent scanning of the firstfiber link in two directions (e.g., along the x-axis and the y-axis bothof which are orthogonal to the longitudinal axis) such that light fromthe first fiber link can be directed to pixels defining an arrayparallel to the x-axis and y-axis and perpendicular to the longitudinalaxis (i.e., the z-axis).

The plurality of actuation elements can be fabricated using a pluralityof piezoelectric tube stacks and can be arrayed surrounding the firstfiber link. Additional description related to piezoelectric tube stacksis provided in relation to FIGS. 9A-9F. In addition to mechanicalconstraint of the base with respect to the retention collar, theactuation elements 810 can be used to control the distance between thebase and the retention collar 130, which is disposed a predetermineddistance along the longitudinal axis from the base. The first fiber linkand the plurality of actuation elements are joined to the retentioncollar. The first fiber link passes through the retention collar in thedirection parallel to the longitudinal axis.

Referring to FIG. 8A, the actuation elements can include a firstpiezoelectric element positioned on a first side of the first fiber linkand operable to contract/expand and a second piezoelectric elementpositioned on a second side of the first fiber link opposing the firstside and operable to expand/contract in opposition to the firstpiezoelectric element. These motions will result in tilting of theretention collar around a first axis orthogonal to the line connectingthe first piezoelectric element and the second piezoelectric element.Moreover, a third piezoelectric element can be positioned on a thirdside of the first fiber link and operable to contract/expand. This thirdpiezoelectric element is paired with a fourth piezoelectric element thatis positioned on a fourth side of the first fiber link opposing thethird side and operable to expand/contract in opposition to the thirdpiezoelectric element. Motion of the third and fourth piezoelectricelements will result in tiling of the retention collar around a secondaxis orthogonal to the line connecting the third piezoelectric elementand the fourth piezoelectric element.

Using the actuation elements as described above to operate themulti-element fiber scanner, the first fiber link can be scanned to movean electromagnetic radiation point along an axis parallel to the baseplane. In this embodiment, the scanning functionality is built into themechanical supports, for example, with piezoelectric actuatorsfunctioning as servo elements (e.g., pistons).

Although the actuation elements are illustrated as cylindrical in theembodiment illustrated in FIG. 8A, this particular shape is not requiredby the present invention and other cross-sections, includingrectangular, square, hexagonal, and the like are included within thescope of the present invention. The cross-section of the actuationelements may be uniform along the length of the actuation elements ornon-uniform.

FIG. 8B is a simplified flowchart illustrating a method of operating amulti-axis fiber scanner according to an embodiment of the presentinvention. The method 850 of operating the multi-element fiber scannerincludes providing a source of electromagnetic radiation (860) anddirecting electromagnetic radiation from the source through a firstfiber link (862). The first fiber link passes through a base having abase plane and along a longitudinal axis orthogonal to the base plane.The method also includes supporting a retention collar disposed apredetermined distance along the longitudinal axis from the base (864).A plurality of piezoelectric actuators join the base and the retentioncollar. As illustrated in FIG. 8A, a first piezoelectric actuator of theplurality of piezoelectric actuators joins one side of the base to oneside of the retention collar and a second piezoelectric actuator of theplurality of piezoelectric actuators joins an opposing side of the baseto an opposing side of the retention collar. The first piezoelectricactuator and the second piezoelectric actuator lie in a scanning plane.In some embodiments, the scanning plane may include the centralwaveguide/fiber, but by means of two other actuators, the tip of thefiber may not be restricted to a plane that includes the rest positionsof two opposed piezoelectric actuators and the central waveguide/fiber.Accordingly, one mode of operation is to drive a first pair of opposedactuators at the resonant frequency of the fiber and the remaining(e.g., two) opposed actuators at a lower frequency that can beassociated with the vertical scan frequency. In yet another mode ofoperation, a spiral scan pattern is utilized.

The method further includes actuating the first piezoelectric actuatorof the plurality of piezoelectric actuators to decrease the distancefrom the one side of the base to the one side of the retention collar(866) and actuating the second piezoelectric actuator of the pluralityof piezoelectric actuators to increase the distance from the opposingside of the base to the opposing side of the retention collar (868). Inresponse to these actuations, the method enables the first fiber link tobe scanned in the scanning plane (870).

FIG. 9A is a simplified side view illustrating a multi-section motionactuation element according to an embodiment of the present invention.As illustrated in FIG. 9A, the multi-section element 905 includes afirst piezoelectric element 910 that is coupled to a secondpiezoelectric element 912. The multi-section element 905 can be referredto as a piezoelectric tube stack since several piezoelectric elementsare stacked to form the element. In some embodiments, the firstpiezoelectric element 910 is proximate to the base and the secondpiezoelectric element 912 is positioned at a location distal from thebase. Each of the piezoelectric elements is able to contract or expandand, as illustrated in FIG. 9A, the piezoelectric elements can beoperated such that the lower section contracts/expands while the uppersection expands/contracts. In some embodiments, each piezoelectricelement includes multiple sectors (e.g., 4 sectors) such that one sideof each tube can be contracted while the other side is expanded. Thismode of operation will produce an oscillatory motion as illustrated inFIG. 9B.

FIG. 9B is a simplified side view illustrating an oscillatory motion ofthe multi-section motion actuation element illustrated in FIG. 9Aaccording to an embodiment of the present invention. As the firstpiezoelectric element 910 contracts (920), the second piezoelectricelement 912 expands (922), causing the multi-section motion actuationelement to take on a sigmoid shape. At the next stage of oscillation, asthe first piezoelectric element 910 expands (924), the secondpiezoelectric element 912 contracts (926), causing the multi-sectionmotion actuation element to take on a second sigmoid shape that mirrorsthe first sigmoid shape. By alternately expanding/contracting thepiezoelectric elements making up the sections, the multi-section elementwill oscillate as illustrated by FIG. 9B, forming the illustrated shapeand the horizontal mirror image in an alternating manner.

FIG. 9C is a simplified side view illustrating a multi-element fiberscanner with the multi-element motion actuation element illustrated inFIG. 9A according to an embodiment of the present invention. Asillustrated in FIG. 9C, the use of the multi-section motion elements 905coupling the base 110 to the retention collar 130 reduce the amount ofbending at the locations where the bottoms and tops of the actuationelements join to the base and retention collar, respectively. Because ofthe reduced bending at these points, the stress is reduced and thelifetime and reliability can be improved. As illustrated in FIG. 9C, thevertical distance between the retention collar 130 and the base 110(measured along the longitudinal direction) decreases as the retentioncollar moves horizontally away from the center position in the lateraldirection. For small oscillations of the retention collar 130, themotion of the retention collar will be substantially planar. As theretention collar moves laterally away from the center, although thelongitudinal height may decrease, the motion lies in planes parallel tothe base plane, and the orientation of the retention collar remainssubstantially parallel to the base. Because the retention collar remainsparallel to the base plane as it moves, the tip of the fiber 940 remainsoriented along the longitudinal direction. The field curvatureassociated with the lateral (and longitudinal) motion of the retentioncollar can be taken into account in designing optical systems to producean image of the fiber as it is scanned. Fiber scanners in which thefiber tip tilts away from the center as it moves laterally toward theends of the range of motion necessitate a larger numerical apertureoptical system to efficiently collect and image light from the fiber.The larger numerical aperture requirement generally leads to a larger,more complicated and more costly optical system. The size of the opticalsystem is a significant consideration for optical systems that are to beintegrated into augmented reality glasses. In contrast, embodiments ofthe present invention maintain the fiber tip in a longitudinalorientation because the retention collar is parallel to the base planethroughout the range of motion. As the tip tilts at the end of the rangeof motion, light can be emitted at steep angles, which can result in amore complicated and expensive lens design as a result of the need tocorrect for high levels of field curvature and steep angles. Usingembodiments of the present invention, maintaining the fiber tipdirection as the fiber scans greatly simplifies the complexity and costof the lens. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

FIG. 9D is a simplified perspective view of a piezoelectric motionactuator according to an embodiment of the present invention. Thepiezoelectric motion actuator 955 illustrated in FIG. 9D includes fouractuation inputs (+X, −X, +Y, and −Y) disposed in a cylindrical casing.The fiber optic cable passes through the orifice 957 and by actuation ofthe four actuation inputs, the fiber optic cable can be scanned in twodimensions. In FIG. 9D, contraction of the +X actuation input andexpansion of the −X actuation input causes the piezoelectric motionactuator to tilt toward the +X axis. Although the motion illustrated inFIG. 9D is in two dimensions (i.e., along planes defined by the x-axisand y-axis), embodiments of the can also expand or contract all fouractuation inputs in unison to contract/expand along the z-axis. Thus,embodiments of the present invention provide for both motion in thex-direction and the y-direction, as well as the use of cylindricalactuators that compress/expand in the z-direction.

In addition to the cylindrical motion actuator illustrated in FIG. 9D,the scope of the present invention includes implementations in whichother geometries are utilized for the motion actuator. As an example, inan embodiment, the motion actuator includes a plurality of opposingmotion actuation elements (e.g., piezoelectric elements) that operate inconjunction with each other as a multi-element motion actuator. FIG. 9Eis a simplified end view illustrating a multi-element motion actuatoraccording to an embodiment of the present invention. The viewillustrated in FIG. 9E is aligned with the longitudinal axis. Asillustrated in FIG. 9E, a first motion actuation element 962 positionedon one side of the fiber optic cable 960 and a second motion actuationelement 964 positioned on the opposite side of the fiber optic cable cancontract/expand in concert to cause the fiber optic cable to move in thehorizontal plane. A third motion actuation element 966 positioned on athird side of the fiber optic cable 960 and a fourth motion actuationelement 968 positioned on the opposite side of the fiber optic cable cancontract/expand in concert to cause the fiber optic cable to move in thevertical plane. By actuation of all four motion actuation elements, thefiber can be scanned in two dimensions as appropriate to use in aprojection display. The embodiment illustrated in FIG. 9E can providefor a lighter system by reducing the piezoelectric mass. In addition tothe rectangular geometry illustrated in FIG. 9E, other geometries,including hexagonal, triangular, and the like are included within thescope of the present invention.

Typically, the actuation inputs are driven with a predetermined phaserelationship between the inputs, for example, 90° out of phase, 180° outof phase, or the like. As an example, to achieve the motion illustratedin FIG. 9D, contraction of the +X actuation input and expansion of the−X actuation input can be accomplished by driving these actuation inputsby signals that are 180° out of phase with respect to each other.Referring to FIGS. 9A and 9C, the first piezoelectric element 910 can bedriven as illustrated in FIG. 9D, causing this first element to bendtoward the +X direction. Concurrently, the second piezoelectric element912 can be driven in an opposite manner, i.e., expansion of the +Xactuation input and contraction of the −X actuation input, causing thissecond element to bend toward the −X direction. As a result, the motionillustrated in FIG. 9B can be achieved by the concerted actuation ofthese piezoelectric elements. Thus, the phase relationship between theactuation inputs of each element and the phase relationship between thevarious elements are controlled to achieve the desired motion.

FIG. 9F is a simplified side view illustrating a multi-section motionactuation structure according to an embodiment of the present invention.As illustrated in FIG. 9F, a piezoelectric structure 979 includes twopiezoelectric elements similar to the multi-section element illustratedin FIG. 9A. The piezoelectric structure 979 can be referred to as apiezoelectric tube stack since two piezoelectric elements (also referredto as piezoelectric motion actuators) are stacked to form the structurein this embodiment. The lower portion of the piezoelectric structure 979is attached to a fixed base, enabling the top of the structure to movein response to the electrode drive voltages. Comparing FIGS. 9A, 9D, and9F, the single piezoelectric element illustrated in FIG. 9D would bestacked together with a second piezoelectric element to form the tubestack illustrated in FIGS. 9A and 9F. For purposes of clarity, theactuation inputs (see FIG. 9D) on the outside surfaces of thepiezoelectric elements are omitted and the electrodes connected to theactuation inputs are illustrated. The interior of the piezoelectricelements are metallized and connected to ground. As described herein,four phases are applied to the actuation inputs arranged at 90°orientations with respect to each other around the outside surfaces ofthe piezoelectric elements.

Although a tube stack is discussed in relation to FIG. 9F, embodimentsof the present invention are not limited to multi-piezoelectric elementimplementations. In some embodiments, a monolithic multi-sectionpiezoelectric element having a lower section and an upper section can beutilized that is fabricated from a monolithic piezoelectric tube.According to an alternative embodiment, a fiber optic with modulatedlight can pass through the piezoelectric structure 979. Thus, thesepiezoelectric structures are useful not only for mechanicalfunctionality but for light delivery as well.

Signal generator 970 provides outputs that are connected to electrodes973 and 975, which are, in turn, connected to corresponding actuationinputs (e.g., +Y, and −Y in FIG. 9D). Signal generator 970 is alsoconnected to a first 90° phase shifter 971 and a second 90° phaseshifter 972, which are connected to electrodes 974 and 976, which are,in turn connected to corresponding actuation inputs (e.g., +X and −X inFIG. 9D). Thus, the signal generator, in concert with the phase shiftersprovides four phases that are 90° out of phase with respect to eachother.

At the intersection 980 of the first and second piezoelectric elements,the electrodes form a helix structure that shifts the position of theelectrode by 180°. This helix structure enables a 180° interchange ofthe piezoelectric drive electrodes at the intersection 980, whichcorresponds to the inflection point of the S-curve. Accordingly, forexample, electrode 974, which is in contact with the actuation input inregion 977 (i.e., the left side of the first piezoelectric element)shifts to be in contact with the actuation input in region 978 (i.e.,the right side of the second piezoelectric element). Similar 180° shiftsof the electrode position occur for the other electrodes, resulting inthe electrodes contacting the right/left or front/back sides of thefirst piezoelectric element also contacting the left/right or back/frontsides of the second piezoelectric element. As an example, the phaseshift between electrodes for the first piezoelectric element can bedefined as 0° for electrode 973 (i.e., front actuation input), 90° forelectrode 974 (left actuation input), 180° for electrode 975 (i.e., backactuation input), and 270° for electrode 976 (i.e., right actuationinput).

In operation, the field is applied radially from the actuation inputs onthe outer surface of the piezoelectric element to the common groundedelectrode on the inner surface of the piezoelectric element. Because theleft/right and front/back actuation inputs are driven by electrodes thatare 180° out of phase, contraction of the left/front side of thepiezoelectric element and expansion of the right/back side of thepiezoelectric element. In the embodiment illustrated in FIG. 9F, thepresence of the helix structure at intersection 980 results in opposingactuation inputs on the two piezoelectric elements to respond in thesame manner. For example, since the +X actuation input on the firstpiezoelectric element and the −X actuation input on the secondpiezoelectric element are connected to the same electrode (e.g.,electrode 974), they will both contract/expand in unison. Accordingly,S-curve operation as illustrated in FIG. 9B results from the electrodedrive configuration illustrated in FIG. 9F in the case that region 977contracts and region 978 contracts in response to the voltage present onelectrode 974. Since the electrodes on the opposite side of thepiezoelectric elements are 180° out of phase, expansion of the regionsopposing regions 977 and 978 will contribute to the S-curve operation.

As the voltages applied to the four actuation inputs of each actuationinput are varied as a function of time, the free end 981 of the secondpiezoelectric element can sweep out a circle lying in a planeperpendicular to the longitudinal direction (i.e., the z-direction).

Referring once again to FIG. 8A and FIGS. 9A-9F, in some embodiments,one or more of the fiber links can be replaced with motion actuationlinks, for example, incorporating the multi-section motion actuationelements illustrated in FIG. 9A. Accordingly, an embodiment of thepresent invention provides a multi-element fiber scanner for scanningelectromagnetic imaging radiation. The multi-element fiber scannerincludes a base having a base plane and a longitudinal axis orthogonalto the base plane and a first fiber link passing through the base in adirection parallel to the longitudinal axis. The first fiber link isoperatively coupled to at least one electromagnetic radiation source.

The multi-element fiber scanner also includes a plurality of motionactuation links joined to the base and extending from the base. Each ofthe plurality of motion actuation links includes a first piezoelectricelement proximate to the base and a second piezoelectric element coupledto the first piezoelectric element at a location distal from the base.The multi-element fiber scanner further includes a retention collardisposed a predetermined distance along the longitudinal axis from thebase. The first fiber link and the second piezoelectric element of eachof the plurality of motion actuation links are joined to the retentioncollar.

FIG. 10 is a multi-element fiber scanner for scanning electromagneticimaging radiation according to an embodiment of the present invention.The multi-element fiber scanner 1000 can be used in a display that scanselectromagnetic imaging radiation and includes a base 1005 having asupport surface 1011 (lower surface of base 1005) defining a base plane,a mounting surface 1007 opposing the support surface 1011, and alongitudinal axis orthogonal to the base plane. The multi-element fiberscanner also includes a plurality of motion actuators 1009 coupled tothe support surface 1011 of the base 1005.

A multi-link fiber structure is coupled to the mounting surface 1007.The multi-link fiber structure includes a fiber base 1010, which can besimilar to base 110 and a fiber link 1014 passing through the fiber base1010 in a direction parallel to the longitudinal axis. The fiber link1014 is operatively coupled from at least one electromagnetic radiationsource (not shown) to the distal (top in the perspective of FIG. 10) endof the fiber link 1014.

The multi-link fiber structure also includes a plurality of motionactuation elements 1040 (e.g., piezoelectric actuation elements) joinedto the fiber base 1010 and extending from the fiber base 1010 along thelongitudinal axis and a retention collar 1030 disposed a predetermineddistance along the longitudinal axis from the fiber base. The fiber link1014 and the plurality of motion actuation elements 1040 are joined tothe retention collar 1030.

In an embodiment, one or more of the plurality of motion actuationelements 1040 are replaced with additional links coupled toelectromagnetic radiation sources. Moreover, a number of additionallinks coupled to the same or a different source of electromagneticradiation can be utilized to simultaneously output multiple pixels for amulti-pixel display.

Actuation of the base 1005 using the plurality of motion actuators 1009acting as pistons results in tilting of the base around the axes of thebase 1005. Tilting can be around a single axis or around multiple axes.In some embodiments, tilting of the base and actuation of the motionactuation elements to tilt the retention collar provide for control ofthe movement, e.g., oscillation, of the fiber link to direct lightemitted from the fiber link toward a display screen.

In some configurations, translation and/or tilting of the retentioncollar can provide scanning of the fiber link in a first direction andtilting of the base can provide for scanning of the fiber link in asecond direction, which can be orthogonal to the first direction. In anembodiment, the first direction is a fast direction (analogous to thehorizontal scan of a raster scanned display) and the second direction isa slow direction (analogous to the vertical scan rate of a rasterscanned display). As an example, the retention collar could beoscillated in the transverse direction and the base could be tilted inthe lateral direction. In addition to tiling of the base, the base canbe translated in the longitudinal direction by expanding/contracting allof the motion actuators in unison.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A multi-element fiber scanner for scanningelectromagnetic imaging radiation, the multi-element fiber scannercomprising: a base having a base plane and a longitudinal axisorthogonal to the base plane; a first fiber link passing through thebase in a direction parallel to the longitudinal axis, wherein the firstfiber link is operatively coupled to at least one electromagneticradiation source; a plurality of additional links, each spatiallyseparated by an air gap, joined to the base, and extending from thebase, wherein the first fiber link passes through the base independentlyfrom the plurality of additional links and the first fiber link and eachof the plurality of additional links are spatially separated by airgaps; and a retention collar disposed a predetermined distance along thelongitudinal axis from the base, wherein the first fiber link and theplurality of additional links are separately joined to the retentioncollar.
 2. The multi-element fiber scanner of claim 1 wherein the firstfiber link passes through the retention collar in the direction parallelto the longitudinal axis.
 3. The multi-element fiber scanner of claim 1further comprising a piezoelectric actuator mechanically coupled to thebase and operable to translate the base in the base plane.
 4. Themulti-element fiber scanner of claim 3 wherein the retention collar isoperable to translate in a set of planes parallel to the base plane. 5.The multi-element fiber scanner of claim 1 wherein one or more of theplurality of additional links pass through the base parallel to thelongitudinal axis and are operatively coupled to the at least oneelectromagnetic radiation source.
 6. The multi-element fiber scanner ofclaim 1 wherein the plurality of additional links are arrayedsurrounding the first fiber link.
 7. The multi-element fiber scanner ofclaim 1 wherein the plurality of additional links extend from the basein the direction parallel to the longitudinal axis.
 8. The multi-elementfiber scanner of claim 1 wherein the plurality of additional linksextend from the base at an angle tilted towards the first fiber link. 9.The multi-element fiber scanner of claim 8 wherein the retention collaris operable to translate along a curved arc.
 10. The multi-element fiberscanner of claim 8 wherein the first fiber link is operable to emit theelectromagnetic imaging radiation toward a focal point.
 11. A method ofoperating a multi-element fiber scanner, the method comprising:providing a source of electromagnetic radiation; directingelectromagnetic radiation from the source of electromagnetic radiationthrough a first fiber link, wherein the first fiber link passes througha base having a base plane and a longitudinal axis orthogonal to thebase plane; supporting a retention collar disposed a predetermineddistance along the longitudinal axis from the base, wherein a pluralityof additional links that are each spatially separated by an air gapseparately join the base and the retention collar, wherein the firstfiber link passes through the base independently from the plurality ofadditional links and the first fiber link and each of the plurality ofadditional links are spatially separated by air gaps; translating thebase in the base plane; translating the retention collar in a set ofplanes parallel to the base plane; and scanning the electromagneticradiation in one or more axes.
 12. The method of claim 11 whereintranslating the base in the base plane comprises actuating the base in afirst direction and actuating the base in a second direction orthogonalto the first direction.
 13. The method of claim 11 wherein translatingthe retention collar in the set of planes parallel to the base planecomprises tilting the plurality of additional links.
 14. The method ofclaim 11 wherein one or more of the plurality of additional links passthrough the base, the method further comprising directing theelectromagnetic radiation from the source of electromagnetic radiationthrough the one or more of the plurality of additional links.
 15. Themethod of claim 11 wherein the electromagnetic radiation is modulated inintensity.
 16. A multi-element fiber scanner for scanningelectromagnetic imaging radiation, the multi-element fiber scannercomprising: a base having a base plane and a longitudinal axisorthogonal to the base plane; a first fiber link passing through thebase in a direction parallel to the longitudinal axis, wherein the firstfiber link is operatively coupled to at least one electromagneticradiation source; a plurality of actuation elements joined to the baseand extending from the base along the longitudinal axis, wherein: eachof the plurality of actuation elements is spatially separated by an airgap; and the first fiber link passes through the base independently fromthe plurality of actuation elements and the first fiber link and each ofthe plurality of actuation elements are spatially separated by air gaps;and a retention collar disposed a predetermined distance along thelongitudinal axis from the base, wherein the first fiber link and theplurality of actuation elements are separately joined to the retentioncollar.
 17. The multi-element fiber scanner of claim 16 wherein thefirst fiber link passes through the retention collar in the directionparallel to the longitudinal axis.
 18. The multi-element fiber scannerof claim 16 wherein the plurality of actuation elements comprise aplurality of piezoelectric tube stacks.
 19. The multi-element fiberscanner of claim 16 wherein the plurality of actuation elements comprisea first piezoelectric element positioned on a first side of the firstfiber link and operable to contract/expand and a second piezoelectricelement positioned on a second side of the first fiber link opposing thefirst side and operable to expand/contract in opposition to the firstpiezoelectric element.
 20. The multi-element fiber scanner of claim 16wherein the plurality of actuation elements further comprise a thirdpiezoelectric element positioned on a third side of the first fiber linkand operable to contract/expand and a fourth piezoelectric elementpositioned on a fourth side of the first fiber link opposing the thirdside and operable to expand/contract in opposition to the thirdpiezoelectric element.